[PATCH v8 4/6] PCI/ERR: simplify function pci_dev_set_io_state() with if

[Ethan Zhao]

No function change.

Signed-off-by: Ethan Zhao <haifeng.z...@intel.com>
---
Changes:
 v8: based on Bjorn's code and truth table, simplify the logic of
function pci_dev_set_io_state(), no function change.

 drivers/pci/pci.h | 54 ++++++++++++++++++++---------------------------
 1 file changed, 23 insertions(+), 31 deletions(-)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 455b32187abd..bceb3f108744 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -359,39 +359,31 @@ struct pci_sriov {
 static inline bool pci_dev_set_io_state(struct pci_dev *dev,
                                        pci_channel_state_t new)
 {
-       bool changed = false;
-
        device_lock_assert(&dev->dev);
-       switch (new) {
-       case pci_channel_io_perm_failure:
-               switch (dev->error_state) {
-               case pci_channel_io_frozen:
-               case pci_channel_io_normal:
-               case pci_channel_io_perm_failure:
-                       changed = true;
-                       break;
-               }
-               break;
-       case pci_channel_io_frozen:
-               switch (dev->error_state) {
-               case pci_channel_io_frozen:
-               case pci_channel_io_normal:
-                       changed = true;
-                       break;
-               }
-               break;
-       case pci_channel_io_normal:
-               switch (dev->error_state) {
-               case pci_channel_io_frozen:
-               case pci_channel_io_normal:
-                       changed = true;
-                       break;
-               }
-               break;
+/*
+ *                     Truth table:
+ *                     requested new state
+ *     current          ------------------------------------------
+ *     state            normal         frozen         perm_failure
+ *     ------------  +  -------------  -------------  ------------
+ *     normal        |  normal         frozen         perm_failure
+ *     frozen        |  normal         frozen         perm_failure
+ *     perm_failure  |  perm_failure*  perm_failure*  perm_failure
+ */
+
+       /* Can always put a device in perm_failure state */
+       if (new == pci_channel_io_perm_failure) {
+               dev->error_state = pci_channel_io_perm_failure;
+               return true;
        }
-       if (changed)
-               dev->error_state = new;
-       return changed;
+
+       /* If already in perm_failure, can't set to normal or frozen */
+       if (dev->error_state == pci_channel_io_perm_failure)
+               return false;
+
+        /* Can always change normal to frozen or vice versa */
+       dev->error_state = new;
+       return true;
 }
 
 static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
-- 
2.18.4